Number of 1 Bits（Difficulty: Easy）

題目：

Write a function that takes an unsigned integer and returns the number of ’1' bits it has (also known as the Hamming weight).

For example, the 32-bit integer ’11' has binary representation 00000000000000000000000000001011, so the function should return 3.

實現：

 1 class Solution {  2 public:  3     int hammingWeight(uint32_t n) {  4         int count = 0;  5         while(n)  6  {  7             count++;  8             n = n & (n - 1);  9  } 10         return count; 11  } 12 };